Postmenopausal women are at higher risk of coronary heart disease (CHD) than premenopausal women, even after controlling for age-effects. However, estrogen replacement therapy significantly lowers the risk of CHD in postmenopausal women. With this study, we propose to determine the kinetics of apolipoprotein A-I, the major protein component of high density lipoproteins, in postmenopausal women undergoing a placebo-controlled, randomized treatment with each of the following regimens:a)placebo,b)0.625mg/d conjugated estrogens, and c)0.625mg/d conjugated estrogens.